ARSENIC IN KENTUCKY GROUNDWATER

Arsenic occurs naturally in rocks, soils, water, plants, and animals. It is used as a wood preservative and in paints, dyes, metals, drugs, soaps, semi-conductors, animal feed additives, and herbicides. Waste-disposal sites and landfills may contain arsenic-bearing materials, and coal burning can release it to the atmosphere. Because long-term exposure to arsenic in drinking water has been linked to cancers and other health problems, in 1974 the U.S. Environmental Protection Agency set a maximum contaminant level (MCL) for arsenic in drinking water at 50 ppb. That MCL will be lowered to 10 ppb, effective January 2006.

More than 4400 arsenic measurements at 930 sites were retrieved from the Kentucky Ground-Water Data Repository and were mapped and statistically summarized to evaluate arsenic concentrations in Kentucky groundwater. Only 2 % of the sites yielded concentrations greater than 50 ppb, and only 7 % of the sites yielded concentrations greater than 10 ppb. The distribution of arsenic concentrations reflects bedrock lithology. Regions underlain by sandstone, shale, coal, or poorly consolidated sands and mudstones had the highest concentrations and the most sites with arsenic greater than 10 ppb, whereas regions underlain by carbonate strata had lower concentrations and a smaller range of values. These results show that although some regions have higher arsenic concentrations than others, arsenic rarely exceeds the MCL in Kentucky groundwater.